Device for stripping a wafer from a carrier

ABSTRACT

Device and method for stripping a wafer from a carrier that is connected to the wafer by an interconnect layer. The device includes a receiving means for accommodating the carrier-wafer combination consisting of the carrier and the wafer, a connection release means for breaking the connection provided by the interconnect layer between the carrier and the wafer, and stripping means for stripping the wafer from the carrier, or for stripping the carrier from the wafer. The connection release means operates in a temperature range from 0° to 350° C., especially from 10° to 200° C., preferably from 20° to 80° C., and more preferably at ambient temperature. The method includes the steps of accommodating the carrier-wafer combination on a receiving means, breaking the connection provided by the interconnect layer by a connection release means, and stripping the wafer from the carrier, or stripping the carrier from the wafer by stripping means.

FIELD OF THE INVENTION

The invention relates to a device and a method for stripping a waferfrom a carrier.

BACKGROUND OF THE INVENTION

The back-thinning of wafers is often necessary in the semiconductorindustry and can take place mechanically and/or chemically. For purposesof back-thinning, in general the wafers are temporarily fixed on acarrier, there being various methods for the fixing. As carriermaterial, for example, films, glass substrates or silicon wafers can beused.

Depending on the carrier materials used and the interconnect layer usedbetween the carrier and the wafer, different methods for dissolving ordestroying the interconnect layer are known, such as, for example, theuse of UV-light, laser beams, temperature action or solvents.

Stripping increasingly constitutes one of the most critical processsteps since thin substrates with substrate thicknesses of a few μmeasily break during stripping/peeling or are damaged by the forces thatare necessary for the stripping process.

Moreover, thin substrates have hardly any stability of shape or none atall and typically curl without support material. During handling of theback-thinned wafer, therefore, fixing and support of the wafer areessentially indispensable.

DE 10 2006 032 488 B4 describes a method for heating the bondingsubstance by means of laser light, the connecting action of the bondingsubstance being neutralized by the associated considerable temperatureincrease to 400 to 500° C. Thus, the problem of heating the entire waferstack (see there: [0021]) is solved. At least the edge region and—due togood thermal conductivity of the wafer material—also the region adjacentto the edge region are, however, subjected to a considerable temperatureincrease. The problem here is also the resulting temperature gradient.

SUMMARY OF THE INVENTION

Therefore, the object of this invention is to devise a device and amethod to detach a wafer from a carrier as nondestructively as possible.

This object is achieved with the features of the independent claims.Advantageous further developments of the invention are given in thedependent claims. The framework of the invention also encompasses allcombinations of at least two of the features given in the specification,the claims, and/or the figures. In the specified value ranges, valuesthat lie within the indicated limits will also be disclosed as boundaryvalues and they are to be claimed in any combination.

The invention is based on the idea of devising a device with whichstripping is enabled at a temperature of less than 350° C. It has beenfound that the temperature ranges above 350° C. can be harmful to thewafer. For higher temperatures, moreover, more energy is required sothat the device according to the invention requires less energy todetach the wafer from the carrier.

Accordingly, the device according to the invention for stripping a waferfrom a carrier that is connected to the wafer by an interconnect layercan be characterized by the following features:

-   -   a receiving means for accommodating a carrier-wafer combination        consisting of the carrier and the wafer,    -   a connection release means for unfixing, in particular breaking        the connection provided by the interconnect layer between the        carrier and the wafer, and    -   stripping means for stripping the wafer from the carrier, or for        stripping the carrier from the wafer,    -   the connection release means being made to work in a temperature        range from 0 to 350° C., especially from 10 to 200° C.,        preferably from 20 to 80° C., and more preferably at ambient        temperature.

Furthermore, according to the invention, a method for stripping a waferfrom a carrier that is connected to the wafer by an interconnect layercan have the following steps:

-   -   accommodating a carrier-wafer combination consisting of the        carrier and the wafer on a receiving means,    -   unfixing, in particular breaking the connection provided by the        interconnect layer between the carrier and the wafer by a        connection release means, and    -   stripping the wafer from the carrier, or for stripping the        carrier from the wafer by stripping means.    -   the connection release means working in a temperature range of        up to 350° C., especially from 10 to 200° C., preferably from 20        to 80° C., and more preferably at ambient temperature.

A wafer is defined as a product substrate, for example a semiconductorwafer, which conventionally is thinned to a thickness of between 0.5 μmand 250 μm, the trend being toward thinner and thinner productsubstrates.

The carrier is, for example, a carrier substrate with a thickness ofbetween 50 μm and 5,000 μm.

The interconnect layer can be an adhesive, for example a solubleadhesive, especially a thermoplastic, which is applied, for example,selectively in an edge region of the carrier-wafer combination,especially in an edge zone from 0.1 to 20 mm. Alternatively, theadhesive can be applied over the entire surface, and the adhesive forcecan be reduced in the center by an adhesion-reducing layer, for examplea fluoropolymer, preferably Teflon.

The receiving means is especially suitably a chuck, especially a spinnerchuck for accommodating the carrier-wafer combination, especially bymeans of negative pressure, for example suction paths, holes or suctioncups. Alternatively, a mechanical accommodation, for example by lateralclamps, is conceivable.

The stripping means can be an upper substrate receiver, for example arelease chuck, preferably by application of negative pressure, forexample suction paths, holes or suction cups.

In one advantageous embodiment of the invention, it is provided that theconnection release means is made to work essentially without heating. Inthis way, it is possible to omit any heating means.

In another advantageous embodiment of the invention, it is provided thatthe connection release means comprises fluid means, especially a solventthat selectively dissolves the interconnect layer, for detaching theinterconnect layer. Chemical dissolution of the interconnect layer isespecially protective of the wafer, and, with the corresponding materialchoice, dissolution can also take place very quickly, especially whenonly edge regions of the wafer are provided with an interconnect layer,so that the solvent can act very quickly from the side. In this way,perforations in the carrier substrate and/or product substrate can beomitted.

In one alternative embodiment of the invention, it is provided that theconnection release means comprises mechanical separating means,especially a blade for cutting through the interconnect layer, fordetaching the interconnect layer. In this way, especially fastseparation of the wafer from the carrier is possible. A combination ofmechanical separation means and fluid means is also conceivable.

In another alternative embodiment of the invention, it is provided thatthe connection release means comprises a UV light source for detachingthe interconnect layer. This embodiment can also be combined with theembodiment of the mechanical separating means and/or the embodiment withfluid means.

To the extent the connection release means is made to act especiallyexclusively from one side edge of the carrier-wafer combination, actionon the wafer and/or the carrier from the top and/or bottom, especiallythe inside region of the wafer that lies within the side edge, can beomitted.

There being a rotation means for rotation of the carrier-wafercombination makes it possible to omit an arrangement of the connectionrelease means over the entire periphery of the carrier-wafercombination, and partial action on the periphery of the carrier-wafercombination is sufficient.

Advantageously, the connection release means has at least one releasedevice that encompasses the side edge, struck especially on thereceiving means and/or the stripping means, preferably forming a seal.By the release device encompassing the side edge of the carrier-wafercombination, especially effective action on the interconnect layer ispossible. Moreover, the release device is used to protect the wafer,especially to protect the side edge. Furthermore, the measure ofencompassing can prevent the fluid means from emerging from the releasedevice or the UV light intensity from being lost. When using mechanicalseparating means, possible impurities are prevented from escaping fromthe release device and from contaminating the wafer. The release devicecan be made U-shaped in cross-section in one advantageous configuration.

To the extent the connection release means, especially the releasedevice, has a working chamber that is preferably sealed to the vicinity,the aforementioned advantages can be still better implemented,especially when using fluid means.

In another advantageous configuration of the invention, it is providedthat the working chamber is made to accommodate a peripheral sector ofthe side edge of the carrier-wafer combination.

Advantageously, the working chamber extends only slightly over the sideedge of the carrier-wafer combination in the direction of the center ofthe wafer, especially up to the receiving direction on the carrier sideand up to the stripping means on the wafer side.

Advantageously, the stripping means are made able to rotate, especiallyare driven by means of the rotary receiving means.

To the extent the connection release means has detergents for cleaningthe wafer, at the same time with stripping of the wafer, the latter canbe cleaned at least in the region exposed to the interconnect layer.

The method according to the invention is improved in that theinterconnect layer in the region of one side edge of the carrier-wafercombination is made adhesive and in one inner region, formed especiallyfrom a fluoropolymer, preferably making contact solely with the wafer,is made less adhesive to nonadhesive at least in the direction of thewafer.

Other advantages, features and details of the invention will becomeapparent from the following description of preferred embodiments andusing the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic of the device according to the invention in afirst process step according to the invention;

FIG. 2 shows a schematic of the device according to the invention in asecond process step according to the invention;

FIGS. 3 a, 3 b, 3 c show a schematic detail view of the release deviceaccording to the invention in a second process step according to theinvention;

FIGS. 4 shows a schematic detail view of the release device according tothe invention in a third process step according to the invention;

FIG. 5 shows a schematic of the device according to the invention in acleaning step for cleaning a carrier according to the invention, and

FIG. 6 shows a schematic of the device according to the invention in onealternative embodiment.

In the figures, the same components and components with the samefunction are identified with the same reference number.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows—roughly in the middle—a carrier-wafer combination 21 thatconsists of at least one wafer 4 and a carrier 1, and that is held on areceiving means 6, especially a chuck, in a horizontal receiving plane Athat is formed by the receiving means. The carrier-wafer combination 21can also be placed, turned by 180°, on the receiving means 6, i.e., withthe carrier 1 down and the wafer 4 up. The carrier-wafer combination 21is supplied by way of a robot arm that is not shown.

According to one especially advantageous embodiment, the receiving means6 or the device is shown relative to the horizontal so that thereceiving plane A is no longer shown horizontally, but rather has a tiltangle to the horizontal that is between 5° and 90°, especially 25° to90°, preferably 45° to 90°, and even more preferably exactly 90°.

The carrier-wafer combination 21 here furthermore consists of aninterconnect layer 3 and an adhesion-reducing layer 2 that is integratedinto the interconnect layer 3, and said layer 2 is arranged in thedirection of the carrier 1 in an inner region 22 of the carrier-wafercombination 21. Outside of the inner region 22, the interconnect layer 3projects above the adhesion-reducing layer 2 on one side edge 23 of thecarrier-wafer combination 21. The side edge 23 is thus an annularsection, and it extends from the outside contour of the carrier-wafercombination 21 or of the carrier 1 to the center of the carrier-wafercombination 21, in a width from 0.1 mm to 20 mm. The wafer 4 typicallyhas a diameter of 300 mm.

The wafer 4, before supply to the device according to the invention, hasusually undergone further treatment steps, for example back-thinning toa thickness of 0.5 μm to 250 μm.

The carrier-wafer combination 21 rises above the receiving means 6 atleast around the side edge 23. The receiving means 6 accordingly has asmaller diameter than the carrier-wafer combination 21 or the wafer 4and/or the carrier 1.

The carrier-wafer combination 21 is fixed on the receiving means 6 bynegative pressure in the conventional manner, the receiving means 6being able to rotate by way of a drive motor 5 and a drive shaft 5 wthat connects the receiving means 6 to the drive motor 5.

The drive motor 5 and the drive shaft 5 w can be made as a hollow shaftwith vacuum supply in order to be able to advantageously connect thevacuum supply to the rotating receiving means 6.

The carrier-wafer combination 21 is housed in a process chamber 7, thedrive motor 5 being located outside of the process chamber 7 and thedrive shaft 5 w being made to penetrate an opening located in the bottom24 of the process chamber.

There is furthermore a drain 8 in the bottom 24.

Laterally from the carrier-wafer combination 21, there is a releasedevice 16 that extends over part of the periphery of the carrier-wafercombination 21. The release device 16 is made U-shaped in cross-sectionand the legs 25, 26 of the release device and one side wall 27 of therelease device 16 surround a working chamber 28 that is made open towardthe carrier-wafer combination 21. The release device extends over acircular ring segment of the carrier-wafer combination 21 and the legs25, 26 rise above the side edge 23 in a release position that is shownin FIG. 2 and that corresponds to the second process step of the methodaccording to the invention. To the extent the receiving plane A istilted, the release device can be made like an immersion bath; thisgreatly simplifies handling of the device.

The release device 16 can be moved by means of an actuator 18 from therelease position into an initial position according to FIG. 1 by way ofan L-shaped actuator arm 29 that projects into the process chamber 7.

Above the carrier-wafer combination 21, there are stripping means forstripping the carrier 1 from the wafer 4, the stripping means having awafer receiver 9, here a chuck.

The wafer receiver 9 is supported on a wafer receiver actuator arm 30with a capacity to rotate in a wafer receiver support 15 of the waferreceiver actuator arm 30, the wafer receiver support 15 being made as anaxial and radial bearing. The wafer receiver support 15 and the waferreceiver 9 are arranged with their axis of rotation flush to the axis ofrotation of the drive shaft 5 w or the receiving means 6.

The stripping means furthermore have elastic suction cups 14 that areintegrated into the wafer receiver 9 and that are made here as bellows.The suction cups 14 are connected to a pressure line 10 that isconnected in turn to a vacuum means. Thus, the carrier 1 in the regionof the suction cups 14 can be sucked onto the wafer receiver 9.

Furthermore, the device according to the invention as shown in FIG. 1has a solvent line 19 that is connected via a solvent actuator arm 31 toa solvent actuator 20 for cleaning the wafer 4 after stripping thecarrier from the wafer 4.

With a sensor that is intended for distance measurement and that isintegrated into the wafer receiver 9, the stripping of the carrier 1from the wafer 4 can be measured, specifically by way of a sensor line12.

After receiving the carrier-wafer combination 21 according to FIG. 1,the wafer receiver 9 is lowered by the wafer receiver actuator 11 ontothe carrier 1 until the suction cups 14 rest on the carrier 1.

Then, a vacuum is applied to the suction cups 14 via the pressure line10; this is shown by an arrow 32.

Thus, the wafer receiver 9 is mechanically connected to thecarrier-wafer combination 21 and the receiving means 6 so that by thedrive motor 5, rotation of the receiving means 6, of the wafer receiver9 and of the carrier-wafer combination 21 that is located in between canbe effected. Rotation is shown by the rotary arrow 33. Alternatively,rotation can take place intermittently, especially by alternate pivotingmotion with a limited angle between 90° and 360°, and by the pivotingmotion, the periphery of the carrier-wafer combination 21 will be moreor less completely detectable by the release device 16.

During continuous rotation, a rotary shaft can be advantageouslyprovided for supply to the wafer receiver 9 for the pressure line 10 andthe sensor line 12.

Then, the release device 16 is moved by the release device actuator 20into the release position that is shown in FIG. 2 and that is also shownin an enlarged extract located at the top right in FIG. 2.

Then, the solvent 34 is delivered via the fluid line 17 into the workingchamber 28 of the release device 16, where the solvent 34 comes intocontact with the interconnect layer 3 in the region of the side edge 23and leads to dissolution of the interconnect layer 3 from the side.

The working chamber 28 can be sealed by contact of the release device16, especially of the legs 25 and 26 with their faces 35 and 36, againstthe receiving means 6, or the wafer receiver 9 can be sealed to thevicinity.

Sealing is conversely not critically necessary, but leads to cuttingdown on the solvent 34.

The progress of dissolving of the interconnect layer 3 in the region ofthe side edge 23 is shown in FIGS. 3 a, 3 b and finally 3 c.

When almost complete dissolution of the edge region of the interconnectlayer 3 that is shown in FIG. 3 c as far as the adhesion-reducing layer2 is achieved, the wafer 4 is raised off the carrier 1 by the suctioncups 14 made as bellows, since the adhesion-reducing layer 2 does notapply sufficient adhesive force compared to the drawing force that isacting due to the suction cups 14. The sensor 13 that measures thedistance of the carrier 1 to the wafer receiver 9 establishes that thecarrier 1 is stripped from the wafer 4 (see FIG. 4), so that the supplyof solvent 34 into the working chamber 28 can be stopped and the releasedevice 16 can be moved by the release device actuator 20 into theinitial position shown in FIG. 5.

Then, the carrier 1 is raised by the wafer receiver actuator 11 in orderto enable cleaning of the wafer 4 by means of the solvent line 19. Thesolvent 37 that has been applied by way of the solvent line 19 isremoved after the wafer 4 is cleaned by rotation of the wafer 4.

Then, the wafer 4 can be supplied by a robot arm to additional devicesand process steps, and the device according to the invention can beloaded with a new carrier-wafer combination 21.

FIG. 6 shows one alternative embodiment of the device according to theinvention that is suitable for processing a carrier-wafer combination 21that has been applied to a foil 38 as described in principle above.

This is because the foil 38 is held by a film frame 39 that makeslateral access to the carrier-wafer combination 21 in theabove-described manner difficult.

Therefore, in the embodiment according to FIG. 6, the release device 16consists of an especially unsupported solvent line 40 with one output 41that is located in the region of the side edge 23 of the carrier-wafercombination 21. In the process step of stripping, the interconnect layer3 on the side edge 23 can be exposed to the solvent.

To detach the wafer 4 that has been fixed on the foil 38 and the filmframe 39, the stripping means for stripping the wafer from the carrierin addition to the wafer receiver 9 have a film frame receiver 42.

The film frame receiver 42 is located between the wafer receiver 9 andthe wafer receiver actuator arm 30 and is connected to the vacuum thatprevails on the pressure line 10. The film frame receiver 42 has suctioncups 43 that can suction the film frame 39 and that are located on theperiphery of the film frame receiver 42.

The function of the suction cups 43 corresponds essentially to thefunction of the suction cups 14.

In another embodiment according to the invention, the carrier-wafercombination 21 consists of a second carrier that is analogouslyconnected to the wafer 4 on the side opposite the carrier 1 via a secondinterconnect layer. In this way, the wafer 4, for example by providingdifferent connecting means in the two interconnect layers andcorrespondingly different solvents, can be placed on another carrier orturned without having to handle the wafer 4 in isolation. The wafer 4 isalways supported by a carrier, either by the carrier 1 or by the secondcarrier.

DESCRIPTION OF THE REFERENCE NUMERALS

-   A Receiving plane-   1 Carrier-   2 Adhesion-reducing layer-   3 Interconnect layer-   4 Wafer-   5 Drive motor-   5 w Drive shaft-   6 Receiving means-   7 Process chamber-   8 Drain-   9 Wafer receiver-   10 Pressure line-   11 Wafer holder receiver-   12 Sensor line-   13 Sensor-   14 Suction cups-   15 Wafer receiver support-   16 Release device-   17 Fluid line-   18 Actuator-   19 Solvent line-   20 Solvent actuator-   21 Carrier-wafer combination-   22 Inner region-   23 Side edge-   24 Bottom-   25 Leg-   26 Leg-   27 Side wall-   28 Working chamber-   29 Actuator arm-   30 Wafer receiver actuator arm-   31 Solvent actuator arm-   32 Arrow-   33 Rotary arrows-   34 Solvent-   35 Face-   36 Face-   37 Solvent-   38 Foil-   39 Film frame-   40 Solvent line-   41 Output-   42 Film frame receiver-   43 Suction cups

Having described the invention, the following is claimed:
 1. Device forstripping a wafer from a carrier, wherein the carrier is fixed to thewafer by an interconnect layer that provides a connection between thecarrier and the wafer, said device comprising: a receiving means forreceiving a carrier-wafer combination comprised of the carrier and thewafer, said interconnect layer providing the connection between thecarrier and the wafer at a peripheral edge of the carrier-wafercombination; a connection release means for unfixing the connectionbetween the carrier and the wafer, said connection release means havingat least one release device that includes: a working chamber forsurrounding at least a portion of the peripheral edge of thecarrier-wafer combination, and means for delivering a solvent to theworking chamber, said solvent for dissolving the interconnect layer; arotation means for rotating the carrier-wafer combination to move theperipheral edge of the carrier-wafer combination through the workingchamber of the connection release means to contact the peripheral edgeof the carrier-wafer combination with the solvent, thereby dissolvingthe interconnect layer at the peripheral edge and breaking theconnection between the carrier and the wafer; and stripping means forstripping the wafer from the carrier, or for stripping the carrier fromthe wafer.
 2. Device according to claim 1, wherein the connectionrelease means operates in a temperature range from 10° C. to 200° C. 3.Device according to claim 1, wherein the connection release meansoperates essentially without heating.
 4. Device according to claim 1,wherein the connection release means further comprises: mechanicalseparating means including a blade for cutting through the interconnectlayer, and for detaching the interconnect layer.
 5. Device according toclaim 1, wherein the connection release means further comprises: a UVlight source for detaching the interconnect layer.
 6. Device accordingto claim 1, wherein the connection release means operates on theperipheral edge of the carrier-wafer combination.
 7. Device according toclaim 1, wherein said at least one release device contacts the receivingmeans and/or the stripping means to seal said working chamber.
 8. Deviceaccording to claim 1, wherein the working chamber is sealed in avicinity of the peripheral edge of the carrier-wafer combination. 9.Device according to claim 8, wherein the working chamber receives asector of the peripheral edge of the carrier-wafer combination. 10.Device according to claim 1, wherein the stripping means is rotatable.11. Device according to claim 1, wherein the interconnect layer is athermoplastic adhesive.
 12. Device according to claim 1, wherein theconnection release means includes a solvent line for supplyingdetergents for cleaning the wafer.
 13. Device according to claim 1,wherein said working chamber has a U-shaped cross-section.
 14. Deviceaccording to claim 13, wherein said working chamber has an open end forreceiving a sector of the peripheral edge of the carrier-wafercombination.
 15. Device according to claim 1, wherein said at least onerelease device includes a side wall and a pair of legs extendingtherefrom to define the working chamber.
 16. Device according to claim15, wherein said pair of legs have respective faces that contact thereceiving means and/or the stripping means to seal said working chamber.17. Device according to claim 1, wherein said rotation means includes arotating shaft.
 18. Device according to claim 1, wherein the connectionrelease means operates in a temperature range from 0° C. to 350° C. 19.Device for releasing an interconnect layer that provides a connectionbetween a carrier and a wafer which forms a carrier-wafer combination,said device comprising: a stripping means for stripping the wafer fromthe carrier, or for stripping the carrier from the wafer; a rotationmeans for rotation of the carrier-wafer combination in a releaseposition; and a connection release means including: a working chamber inwhich at least a section of the peripheral edge of the carrier-wafercombination can be accommodated in the working chamber, and means fordelivering a solvent to the working chamber, said solvent for dissolvingthe interconnect layer at the peripheral edge of the carrier-wafercombination.
 20. Device according to claim 19, wherein the solvent actsat the peripheral edge of the carrier-wafer combination.
 21. Deviceaccording to claim 19, wherein the connection release means comprises animmersion bath.
 22. Device according to one claim 19, wherein theconnection release means has a U-shaped cross section that defines saidworking chamber.
 23. Device according to claim 19, wherein said workingchamber is defined by a pair of legs and a side wall, said workingchamber open towards the carrier-wafer combination.